Astronomy

Webb sees carbon-rich dust grains at redshift, in the first billion years of cosmic time

By ScientifiCult 19 July 2023

Webb sees carbon-rich dust grains at redshift, in the first billion years of cosmic time

For the first time, the NASA/ESA/CSA James Webb Space Telescope has observed the chemical signature of carbon-rich dust grains at redshift ~ 7 [1], which is roughly equivalent to one billion years after the birth of the Universe [2]. Similar observational signatures have been observed in the much more recent Universe, attributed to complex, carbon-based molecules known as polycyclic aromatic hydrocarbons (PAHs). It is not thought likely, however, that PAHs would have developed within the first billion years of cosmic time. Therefore, this observation suggests the exciting possibility that Webb may have observed a different species of carbon-based molecule: possibly minuscule graphite- or diamond-like grains produced by the earliest stars or supernovae. This observation suggests exciting avenues of investigation into both the production of cosmic dust and the earliest stellar populations in our Universe, and was made possible by Webb’s unprecedented sensitivity.

The seemingly empty spaces in our Universe are in reality often not empty at all, but occupied by clouds of gas and cosmic dust. This dust consists of grains of various sizes and compositions that are formed and ejected into space in a variety of ways, including by supernova events. This material is crucial to the evolution of the Universe, as dust clouds ultimately form the birthplaces for new stars and planets. However, it can also be a hindrance to astronomers: the dust absorbs stellar light at certain wavelengths, making some regions of space very challenging to observe. An upside, however, is that certain molecules will very consistently absorb or otherwise interact with specific wavelengths of light. This means that astronomers can acquire information about the cosmic dust’s composition by observing the wavelengths of light that it blocks. An international team of astronomers used this technique, combined with Webb’s extraordinary sensitivity, to detect the presence of carbon-rich dust grains only a billion years after the birth of the Universe.

Joris Witstok of the University of Cambridge, the lead author of this work, elaborates: “Carbon-rich dust grains can be particularly efficient at absorbing ultraviolet light with a wavelength around 217.5 nanometres, which for the first time we have directly observed in the spectra of very early galaxies.”

This prominent 217.5-nanometre feature has previously been observed in the much more recent and local Universe, both within our own Milky Way galaxy, and in galaxies up to redshift ~ 3 [1]. It has been attributed to two different types of carbon-based species: polycyclic aromatic hydrocarbons (PAHs) or nano-sized graphitic grains. PAHs are complex molecules, and modern models predict that it should take several hundreds of millions of years before they form. It would be surprising, therefore, if the team had observed the chemical signature of a mixture of dust grains that include species that were unlikely to have formed yet. However, according to the science team, this result is the earliest and most distant direct signature for this particular type of carbon-rich dust grain.

The answer may lie in the details of what was observed. As already stated, the feature associated with the cosmic dust mixture of PAHs and tiny graphitic grains is at 217.5 nanometres. However, the feature observed by the team actually peaked at 226.3 nanometres. A nanometre is a millionth of a millimetre, and this discrepancy of less than ten nanometres could be accounted for by measurement error [3]. Equally, it could also indicate a difference in the composition of the early-Universe cosmic dust mixture that the team detected.

“This slight shift in wavelength of where the absorption is strongest suggests we may be seeing a different mix of grains, for example graphite- or diamond-like grains,” adds Witstok. “This could also potentially be produced on short timescales by Wolf-Rayet stars or supernova ejecta.”

The detection of this feature in the early Universe is surprising, and allows astronomers to postulate about the mechanisms that could create such a mix of dust grains. This involves drawing on existing knowledge from observations and models. Witstok suggests diamond grains formed in supernova ejecta because models have previously suggested that nano-diamonds could be formed this way. Wolf-Rayet stars are suggested because they are exceptionally hot towards the end of their lives, and very hot stars tend to live fast and die young; giving enough time for generations of stars to have been born, lived, and died, to distribute carbon-rich grains into the surrounding cosmic dust in under a billion years. Models have also shown that carbon-rich grains can be produced by certain types of Wolf-Rayet stars, and just as importantly that those grains can survive the violent deaths of those stars. However, it is still a challenge to fully explain these results with the existing understanding of the early formation of cosmic dust. These results will therefore go on to inform the development of improved models and future observations.

Before Webb, the observations of multiple galaxies had to be combined in order to get signals strong enough to make deductions about the stellar populations in the galaxies, and to learn about how their light was affected by dust absorption. Importantly, astronomers were restricted to studying relatively old and mature galaxies that had had a long time to form stars as well as dust. This limited their ability to really pin down the key sources of cosmic dust. With the advent of Webb, astronomers are now able to make very detailed observations of the light from individual dwarf galaxies, seen in the first billion years of cosmic time. Webb finally permits the study of the origin of cosmic dust and its role in the crucial first stages of galaxy evolution.

“This discovery was made possible by the unparalleled sensitivity improvement in near-infrared spectroscopy provided by Webb, and specifically its Near-Infrared Spectrograph (NIRSpec),” noted team member Roberto Maiolino of the University of Cambridge and University College London. “The increase in sensitivity provided by Webb is equivalent, in the visibile, to instantaneously upgrading Galileo’s 37-millimetre telescope to the 8-metre Very Large Telescope (one of the most powerful modern optical telescopes).”

NIRSpec was built for the European Space Agency by a consortium of European companies led by Airbus Defence and Space (ADS) with NASA’s Goddard Space Flight Centre providing its detector and micro-shutter subsystems. The primary goal of NIRSpec is to enable large spectroscopic surveys of astronomical objects such as stars or distant galaxies. This is made possible by its powerful multi-object spectroscopy mode, which makes use of microshutters. This mode is capable of obtaining spectra of up to nearly 200 objects simultaneously, over a 3.6 × 3.4 arcminute field of view — the first time this capability has been provided from space. This mode makes for very efficient use of Webb’s valuable observing time.

The team is also planning further research into the data and this result.

“We are planning to work further with theorists who model dust production and growth in galaxies,” shares team member Irene Shivaei of the University of Arizona/Centro de Astrobiología (CAB). “This will shed light on the origin of dust and heavy elements in the early Universe.”

These observations were made as part of the JWST Advanced Deep Extragalactic Survey, or JADES, which devoted about 32 days of telescope time to uncovering and characterising faint, distant galaxies. This programme has facilitated the discovery of hundreds of galaxies that existed when the Universe was less than 600 million years old, including some of the farthest galaxies known to date. The sheer number and maturity of these galaxies was far beyond predictions from observations made before Webb’s launch. This new result of early-Universe dust grains contributes to our growing and evolving understanding of the evolution of stellar populations and galaxies during the first billion years of cosmic time.

“This discovery implies that infant galaxies in the early Universe develop much faster than we ever anticipated,” adds team member Renske Smit of the Liverpool John Moores University in the United Kingdom. “Webb shows us a complexity of the earliest birth-places of stars (and planets) that models are yet to explain.“

The results have been published today in Nature.

The infrared image shown here was taken as part of the JADES programme (the JWST Advanced Deep Extragalactic Survey) and shows a portion of an area of the sky known as GOODS-South.
This region was the focus area of Webb study for an international team of astronomers, who observed the chemical signature of carbon-rich dust grains at redshift ~7. This is roughly equivalent to one billion years after the birth of the Universe. Similar observational signatures have been observed in the much more recent Universe, attributed to complex, carbon-based molecules known as polycyclic aromatic hydrocarbons (PAHs). It is not thought likely, however, that PAHs would have developed within the first billion years of cosmic time. Therefore, this observation suggests the exciting possibility that Webb may have observed a different species of carbon-based molecule: possibly minuscule graphite- or diamond-like grains produced by the earliest stars or supernovae. This observation suggests exciting avenues of investigation into both the production of cosmic dust and the earliest stellar populations in our Universe, and was made possible by Webb’s unprecedented sensitivity.
In this image, blue, green, and red were assigned to Webb’s NIRCam (Near-Infrared Camera) data at 0.9, 1.15, and 1.5 microns; 2.0, 2.77, and 3.55 microns; and 3.56, 4.1, and 4.44 microns (F090W, F115W, and F150W; F200W, F277W, and F335M; and F356W, F410M, and F444W), respectively.
Credit:
ESA/Webb, NASA, ESA, CSA, B. Robertson (UC Santa Cruz), B. Johnson (Center for Astrophysics, Harvard & Smithsonian), S. Tacchella (University of Cambridge, M. Rieke (Univ. of Arizona), D. Eisenstein (Center for Astrophysics, Harvard & Smithsonian), A. Pagan (STScI)

Notes

[1] The Universe is expanding. The expansion is taking place at the fundamental spacetime level, which means that light travelling through the Universe is ‘stretched’ as the Universe expands. The earlier in the Universe the light originated, the more it will have been stretched by now. Practically speaking, this stretching of light means its wavelength becomes longer. This effect is known as cosmological redshift, because the colour red has the longest wavelength of all light visible to human eyes. Because of this, cosmological time is often not measured in years, but is indicated by the redshift of the observed light. The very local Universe — where the light we observe was emitted recently and has not been notably redshifted — has a low redshift. Conversely, redshift 7 corresponds to light that was emitted about 13 billion years ago, in the very early Universe.

[2] Astronomy fundamentally involves the study of light, and light travels at a finite speed (roughly 300 million kilometres per second). Objects can only be observed by humans once light from them has reached Earth. Whilst in some ways providing a limitation, this also provides a direct opportunity to study the early as well as the present Universe. Studying light from the early Universe necessarily entails the observation of regions very distant from Earth from which it takes a huge amount of time for light to travel to us. Thus, probing these early cosmological times (or high redshifts) requires very sensitive telescopes.

[3] All scientific measurements — including those from observations and those predicted by models — will have an associated error. This is because there will always be sources of uncertainty. If a measurement falls within the bounds of the expected error, it means that it could still be accurate: in this context, that means the 226.3 nanometre feature could still account for the same mix of cosmic dust as that represented by the 217.5 nanometre feature.

Press release from ESA Webb

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Astronomy

Methyl cation (CH3+) detected in the d203-506 system, in the Orion Nebula

By ScientifiCult 26 June 2023

Webb makes first detection of methyl cation (CH3+), a crucial carbon molecule in a planet-forming disc system known as d203-506, in the Orion Nebula

An international team of scientists have used data collected by the NASA/ESA/CSA James Webb Space Telescope to detect a molecule [1] known as the methyl cation (CH3+) for the first time, located in the protoplanetary disc surrounding a young star. They accomplished this feat with a cross-disciplinary expert analysis, including key input from laboratory spectroscopists. This simple molecule has a unique property: it reacts relatively inefficiently with the most abundant element in our Universe (hydrogen) but reacts readily with other molecules and therefore initiates the growth of more complex carbon-based molecules. Carbon chemistry is of particular interest to astronomers because all known life is carbon-based. The vital role of CH3+ in interstellar carbon chemistry was predicted in the 1970s, but Webb’s unique capabilities have finally made observing it possible — in a region of space where planets capable of accommodating life could eventually form.

Methyl cation CH43+ d203-506 Orion Nebula — An international team of scientists have used data collected by the NASA/ESA/CSA James Webb Space Telescope to detect a molecule known as the methyl cation (CH3+) for the first time, located in the protoplanetary disc surrounding a young star. They accomplished this feat with a cross-disciplinary expert analysis, including key input from laboratory spectroscopists. The vital role of CH3+ in interstellar carbon chemistry has been predicted since the 1970s, but Webb’s unique capabilities have finally made observing it possible — in a region of space where planets capable of accommodating life could eventually form. This graphic shows the area, in the centre of the Orion Nebula, that was studied by the team. The nebula lies about 1350 light-years from Earth. The largest image, on the left, is from Webb’s NIRCam instrument. On the right, the telescope is focused on a smaller area, where the team have used Webb’s MIRI instrument to add more depth to their study. A total of eighteen filters across both the MIRI and NIRCam instruments were used in these images, covering a range of wavelengths from 1.4 microns in the near-infrared to 25.5 microns in the mid-infrared. The detailed coverage was necessary for the team to study the light from protoplanetary discs, and analyse the unique features revealed by Webb using spectroscopy from its MIRI and NIRSpec instruments. The region captured here in breathtaking detail by Webb is a part of the Orion Nebula known as the Orion Bar. It is an ionisation front, where energetic far-ultraviolet light from the Trapezium Cluster — located off the upper-left corner — interacts with dense molecular clouds. The energy of the stellar radiation is slowly eroding the Orion Bar, and this has a profound effect on the molecules and chemistry in the protoplanetary discs that have formed around newborn stars here. At the very centre of the MIRI area is an ionised star-protoplanetary disc system, or proplyd, named d203-506. The pullout at the bottom right displays a combined NIRCam and MIRI image of this young system. Its extended shape is due to pressure from the harsh ultraviolet radiation striking it. The first clear images of proplyds in the Orion Nebula were obtained by the NASA/ESA Hubble Space Telescope, including d203-506. Now Webb’s extended infrared vision adds to the picture, as the team of astronomers were able to confirm that the methyl cation molecule is present in this very proplyd. Credit: ESA/Webb, NASA, CSA, M. Zamani (ESA/Webb), the PDRs4All ERS Team

An international team of scientists have used data collected by the NASA/ESA/CSA James Webb Space Telescope to detect a molecule known as the methyl cation (CH3+) for the first time, located in the protoplanetary disc surrounding a young star. They accomplished this feat with a cross-disciplinary expert analysis, including key input from laboratory spectroscopists. The vital role of CH3+ in interstellar carbon chemistry has been predicted since the 1970s, but Webb’s unique capabilities have finally made observing it possible — in a region of space where planets capable of accommodating life could eventually form. This image is NIRCam’s view of the Orion Bar region studied by the team of astronomers. Bathed in harsh ultraviolet light from the stars of the Trapezium Cluster, it is an area of intense activity, with star formation and active astrochemistry. This made it a perfect place to study the exact impact that ultraviolet radiation has on the molecular makeup of the discs of gas and dust that surround new stars. The radiation erodes the nebula’s gas and dust in a process known as photoevaporation; this creates the rich tapestry of cavities and filaments that fill the view. The radiation also ionises the molecules, causing them to emit light — not only does this create a beautiful vista, it also allows astronomers to study the molecules using the spectrum of their emitted light obtained with Webb’s MIRI and NIRSpec instruments. The two very large, bright stars are two of the three stars in the θ² Orionis system — the Trapezium Cluster is also known as θ¹ Orionis. The brightest star here, θ² Orionis A, is surrounded by particularly bright and red puffs of dust, which are reflecting the star’s light towards Earth. Its great brightness — it is visible with the naked eye — is due to the fact that θ² Orionis A is itself a ternary system made of three closely bound bright stars. There are more proplyds visible in this image than just d203-506 — the Orion Nebula is replete with such new stars. In the very top left, a tiny star is visible within a long, dusty cocoon. This globule has formed from the star’s protoplanetary disc, as the disc is broken down by the energetic radiation of the Trapezium Cluster. Around the globule, a round shockwave is strikingly visible moving through the gas of the Orion Nebula. Credit: ESA/Webb, NASA, CSA, M. Zamani (ESA/Webb), the PDRs4All ERS Team

Carbon compounds [2] form the foundations of all known life, and as such are of a particular interest to scientists working to understand both how life developed on Earth, and how it could potentially develop elsewhere in our Universe. As such, interstellar organic chemistry [3] is an area of keen fascination to astronomers who study the places where new stars and planets form. Molecular ions [4] containing carbon are especially important, because they react with other small molecules to form more complex organic compounds even at low interstellar temperatures [5]. The methyl cation (CH3+) is one such carbon-based ion. CH3+ has been posited by scientists to be of particular importance since the 1970s and 1980s. This is due to a fascinating property of CH3+, which is that it reacts with a wide range of other molecules. This little cation is significant enough that it has been theorised to be the cornerstone of interstellar organic chemistry, yet until now it has never been detected. The unique properties of the James Webb Space Telescope made it the ideal instrument to search for this crucial cation — and already, a group of international scientists have observed it with Webb for the first time. Marie-Aline Martin of Paris-Saclay University, France, a spectroscopist and science team member, explains:

“This detection of CH3+ not only validates the incredible sensitivity of James Webb but also confirms the postulated central importance of CH3+ in interstellar chemistry.”

The CH3+ signal was detected in the star-protoplanetary disc [6] system known as d203-506, which is located about 1350 light years away, in the Orion Nebula. Whilst the star in d203-506 is a small red dwarf star, with a mass only about a tenth of the Sun’s, the system is bombarded by strong ultraviolet radiation from nearby hot, young, massive stars. Scientists believe that most planet-forming protoplanetary disks go through a period of such intense ultraviolet radiation, since stars tend to form in groups that often include massive, ultraviolet-producing stars. Fascinatingly, evidence from meteorites suggest that the protoplanetary disc that went on to form our Solar System was also subject to a vast amount of ultraviolet radiation — emitted by a stellar companion to our Sun that has long since died (massive stars burn brightly and die much faster than less massive stars). The confounding factor in all this is that ultraviolet radiation has long been considered to be purely destructive to the formation of complex organic molecules — and yet there is clear evidence that the only life-supporting planet that we know of was born from a disc that was heavily exposed to it.

The team that performed this research may have found the solution to this conundrum. Their work predicts that the presence of CH3+ is in fact connected to ultraviolet radiation, which provides the necessary source of energy for CH3+ to form. Furthermore, the period of ultraviolet radiation experienced by certain disks seems to have a profound impact on their chemistry. For example, Webb observations of protoplanetary disks that are not subject to intense ultraviolet radiation from a nearby source show a large abundance of water — in contrast to d203-506, where the team could not detect water at all. The lead author, Olivier Berné of the University of Toulouse, France, elaborates,

“This clearly shows that ultraviolet radiation can completely change the chemistry of a proto-planetary disc. It might actually play a critical role in the early chemical stages of the origins of life by helping to produce CH3+ — something that has perhaps previously been underestimated.”

Although research published as early as the 1970s predicted the importance of CH3+, it has previously been virtually impossible to detect. Many molecules in protoplanetary discs are observed using radio telescopes. However, for this to be possible the molecules in question need to possess what is known as a ‘permanent dipole moment’, meaning that the molecule’s geometry is such that its electric charge is permanently off balance, giving the molecule a positive and a negative ‘end’. CH3+ is symmetrical, and therefore its charge is balanced, and so lacks the permanent dipole moment necessary for observations with radio telescopes. It would theoretically be possible to observe spectroscopic lines emitted by CH3+ in the infrared, but the Earth’s atmosphere makes these essentially impossible to observe from Earth. Thus, it was necessary to use a sufficiently sensitive space-based telescope that could observe signals in the infrared. Webb’s MIRI and NIRSpec instruments were perfect for the job. In fact, a CH3+ detection had previously been so elusive that when the team first saw the signal in their data, they were not sure how to identify it. Remarkably, the team were able to interpret their result within four short weeks, by drawing on the expertise of an international team with a varied range of expertise.

The discovery of CH3+ was possible only through a collaboration among observational astronomers, astrochemical modellers, theoreticians, and experimental spectroscopists, which combined the unique capabilities of JWST in space with those of Earth-based laboratories in order to successfully investigate and interpret our local universe’s composition and evolution. Marie-Aline Martin adds:

“Our discovery was only made possible because astronomers, modellers, and laboratory spectroscopists joined forces to understand the unique features observed by James Webb.”

The PDRs4ALL ERS team‘s results have been published today in Nature.

Notes

[1] A molecule is a particle made up of two or more atoms that are held together by chemical bonds.

[2] A compound is a molecule that includes more than one element. Thus, all compounds are molecules but not all molecules are compounds. As an example, the hydrogen molecule (H2) is a molecule but not a compound, whereas the water molecule (H2O) is also a compound.

[3] Organic chemistry refers to the chemistry of carbon-based molecules and compounds. It may also be referred to as carbon chemistry.

[4] An ion is an atom or molecule that has an overall electrical charge, due to an excess or deficit in the number of negative electrons compared to the number of positive protons in the ion. A cation is an ion with a net positive charge (so a deficit of electrons).

[5] A complex organic molecule is a molecule with multiple carbon atoms.

[6] A protoplanetary disc is a rotating disc of gas and dust that forms around young stars, and from which planets can ultimately form.

Press release from ESA Webb.

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Astronomy

Webb finds water in Comet 238P/Read, a rare main belt comet

By ScientifiCult 15 May 2023

Webb finds water, and a new mystery, in Comet 238P/Read, a rare main belt comet

The NASA/ESA/CSA James Webb Space Telescope has enabled another long-sought scientific breakthrough, this time for Solar System scientists studying the origins of the water that has made life on Earth possible. Using Webb’s NIRSpec (Near-Infrared Spectrograph) instrument, astronomers have confirmed gas – specifically water vapour – around a comet in the main asteroid belt for the first time, proving that water from the primordial Solar System can be preserved as ice in that region. However, the successful detection of water comes with a new puzzle: unlike other comets, Comet 238P/Read had no detectable carbon dioxide.

water Comet 238 P/Read — This artist’s concept of Comet 238P/Read shows the main belt comet sublimating—its water ice vapourising as its orbit approaches the Sun. This is significant, as the sublimation is what distinguishes comets from asteroids, creating their distinctive tail and hazy halo, or coma. The NASA/ESA/CSA James Webb Space Telescope’s detection of water vapour at Comet Read is a major benchmark in the study of main belt comets, and in the broader investigation of the origin of Earth’s abundant water.
Credit: NASA, ESA

“Our water-soaked world, teeming with life and unique in the universe as far as we know, is something of a mystery – we’re not sure how all this water got here,” said Stefanie Milam, Webb Deputy Project Scientist for Planetary Science and a co-author on the study reporting the finding. “Understanding the history of water distribution in the Solar System will help us to understand other planetary systems, and if they could be on their way to hosting an Earth-like planet,” she added.

Comet Read is a main belt comet – an object that resides in the main asteroid belt but which periodically displays a halo, or coma, and tail like a comet. Main belt comets themselves are a fairly new classification, and Comet Read was one of the original three comets used to establish the category. Before that, comets were understood to originate in the Kuiper Belt and Oort Cloud, beyond the orbit of Neptune, where their ices could be preserved farther from the Sun. Frozen material that vaporises as they approach the Sun is what gives comets their distinctive coma and streaming tail, differentiating them from asteroids. Scientists have long speculated that water ice could be preserved in the warmer asteroid belt, inside the orbit of Jupiter, but definitive proof was elusive – until Webb.

“In the past we’ve seen objects in the main belt with all the characteristics of comets, but only with this precise spectral data from Webb can we say yes, it’s definitely water ice that is creating that effect,” explained astronomer Michael Kelley of the University of Maryland, lead author of the study.

“With Webb’s observations of Comet Read, we can now demonstrate that water ice from the early Solar System can be preserved in the asteroid belt,” Kelley said.

This image of Comet 238P/Read was captured by the NIRCam (Near-Infrared Camera) instrument on the NASA/ESA/CSA James Webb Space Telescope on 8 September 2022. It displays the hazy halo, called the coma, and tail that are characteristic of comets, as opposed to asteroids. The dusty coma and tail result from the vapourisation of ices as the Sun warms the main body of the comet. Credit: NASA, ESA, CSA, M. Kelley (University of Maryland), H. Hsieh (Planetary Science Institute), A. Pagan (STScI)

The missing carbon dioxide was a bigger surprise. Typically carbon dioxide makes up about 10 percent of the volatile material in a comet that can be easily vaporised by the Sun’s heat. The science team presents two possible explanations for the lack of carbon dioxide. One possibility is that Comet Read did have carbon dioxide when it formed, but has lost that because of warm temperatures.

“Being in the asteroid belt for a long time could do it – carbon dioxide vaporises more easily than water ice, and could percolate out over billions of years,” Kelley said. Alternatively, he said, Comet Read may have formed in a particularly warm pocket of the Solar System, where no carbon dioxide was available.

The next step is taking the research beyond Comet Read to see how other main belt comets compare, says astronomer Heidi Hammel of the Association of Universities for Research in Astronomy (AURA), lead for Webb’s Guaranteed Time Observations for Solar System objects and co-author of the study.

“These objects in the asteroid belt are small and faint, and with Webb we can finally see what is going on with them and draw some conclusions. Do other main belt comets also lack carbon dioxide? Either way it will be exciting to find out,” Hammel said.

Co-author Milam imagines the possibilities of bringing the research even closer to home. “Now that Webb has confirmed there is water preserved as close as the asteroid belt, it would be fascinating to follow up on this discovery with a sample collection mission, and learn what else the main belt comets can tell us.”

The study is published in the journal Nature.

Press release from ESA Webb.

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Genetics

Discovery of world’s oldest DNA breaks record by one million years

By ScientifiCult 7 December 2022

A new chapter in the history of evolution

Discovery of world’s oldest DNA breaks record by one million years

Two-million-year-old DNA has been identified for the first time opening a new chapter in the history of evolution.

Microscopic fragments of environmental DNA were found in Ice Age sediment in northern Greenland. The fragments are one million years older than the previous record for DNA sampled from a Siberian mammoth bone.

The ancient DNA has been used to map a two-million-year-old ecosystem which weathered extreme climate change. The results could help predict the long-term environmental toll of today’s global warming.

The discovery was made by a team of scientists led by Professor Eske Willerslev and Professor Kurt Kjær. Professor Willerslev is a Fellow of St John’s College, University of Cambridge and Director of the Lundbeck Foundation GeoGenetics Centre at the University of Copenhagen where Professor Kjær, a geology expert, is also based.

The results of the 41 usable samples found hidden in clay and quartz are published today in Nature.

“A new chapter spanning one million extra years of history has finally been opened and for the first time we can look directly at the DNA of a past ecosystem that far back in time,” says Willerslev.

“DNA can degrade quickly but we’ve shown that under the right circumstances, we can now go back further in time than anyone could have dared imagine.”

“The ancient DNA samples were found buried deep in sediment that had built-up over 20,000 years,” says Kjær. “The sediment was eventually preserved in ice or permafrost and, crucially, not disturbed by humans for two million years.”

Close-up of organic material in the coastal deposits. The organic layers show traces of the rich plant flora and insect fauna that lived two million years ago in Kap København in North Greenland. Credits: Professor Kurt H. Kjær

The incomplete samples, a few millionths of a millimetre long, were taken from the København Formation, a sediment deposit almost 100 metres thick tucked in the mouth of a fjord in the Arctic Ocean in Greenland’s northernmost point. The climate in Greenland at the time varied between Arctic and temperate and was between 10-17C warmer than Greenland is today. The sediment built up metre by metre in a shallow bay.

Evidence of animals, plants and microorganisms including reindeer, hares, lemmings, birch and poplar trees were discovered. Researchers even found that Mastodon, an Ice Age mammal, roamed as far as Greenland before later becoming extinct. Previously it was thought the range of the elephant-like animals did not extend as far as Greenland from its known origins of North and Central America.

Detective work by 40 researchers from Denmark, the UK, France, Sweden, Norway, the USA and Germany, unlocked the secrets of the fragments of DNA. The process was painstaking – first they needed to establish whether there was DNA hidden in the clay and quartz, and if there was, could they successfully detach the DNA from the sediment to examine it? The answer, eventually, was yes. The researchers compared every single DNA fragment with extensive libraries of DNA collected from present-day animals, plants and microorganisms. A picture began to emerge of the DNA from trees, bushes, birds, animals and microorganisms.

A two million- year-old trunk from a larch tree still stuck in the permafrost within the coastal deposits. The tree was carried to the sea by the rivers that eroded the former forested landscape. Credits: Professor Svend Funder

Some of the DNA fragments were easy to classify as predecessors to present-day species, others could only be linked at genus level, and some originated from species impossible to place in the DNA libraries of animals, plants and microorganisms still living in the 21st century.

The two-million-year-old samples also help academics build a picture of a previously unknown stage in the evolution of the DNA of a range of species still in existence today.

“Expeditions are expensive and many of the samples were taken back in 2006 when the team were in Greenland for another project, they have been stored ever since,” says Kjær.

“It wasn’t until a new generation of DNA extraction and sequencing equipment was developed that we’ve been able to locate and identify extremely small and damaged fragments of DNA in the sediment samples. It meant we were finally able to map a two-million-year-old ecosystem.”

“The Kap København ecosystem, which has no present-day equivalent, existed at considerably higher temperatures than we have today – and because, on the face of it, the climate seems to have been similar to the climate we expect on our planet in the future due to global warming,” says co-first author Assistant Professor Mikkel Pedersen of the Lundbeck Foundation GeoGenetics Centre.

“One of the key factors here is to what degree species will be able to adapt to the change in conditions arising from a significant increase in temperature. The data suggests that more species can evolve and adapt to wildly varying temperatures than previously thought. But, crucially, these results show they need time to do this. The speed of today’s global warming means organisms and species do not have that time so the climate emergency remains a huge threat to biodiversity and the world – extinction is on the horizon for some species including plants and trees.”

While reviewing the ancient DNA from the Kap København Formation, the researchers also found DNA from a wide range of microorganisms, including bacteria and fungi, which they are continuing to map. A detailed description of how the interaction – between animals, plants and single-cell organisms – within the former ecosystem at Greenland’s northernmost point worked biologically will be presented in a future research paper.

It is now hoped that some of the ‘tricks’ of the two-million-year-old plant DNA discovered may be used to help make some endangered species more resistant to a warming climate.

“It is possible that genetic engineering could mimic the strategy developed by plants and trees two million years ago to survive in a climate characterised by rising temperatures and prevent the extinction of some species, plants and trees,” says Kjær. “This is one of the reasons this scientific advance is so significant because it could reveal how to attempt to counteract the devastating impact of global warming.”

The findings from the Kap København Formation in Greenland have opened up a whole new period in DNA detection.

“DNA generally survives best in cold, dry conditions such as those that prevailed during most of the period since the material was deposited at Kap København,” says Willerslev. “Now that we have successfully extracted ancient DNA from clay and quartz, it may be possible that clay may have preserved ancient DNA in warm, humid environments in sites found in Africa.

“If we can begin to explore ancient DNA in clay grains from Africa, we may be able to gather ground-breaking information about the origin of many different species – perhaps even new knowledge about the first humans and their ancestors – the possibilities are endless.”

Bibliographic information:

A 2-million-year-old ecosystem in Greenland uncovered by environmental DNA, Nature (7-Dec-2022), DOI: 10.1038/s41586-022-05453-y

Press release from the University of Cambridge on the discovery of world’s oldest DNA.

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Genetics

Black Death shaped evolution of immunity genes, setting course for how we respond to disease today

By ScientifiCult 19 October 2022

Black Death shaped evolution of immunity genes, setting course for how we respond to disease today

An international team of scientists who analyzed centuries-old DNA from victims and survivors of the Black Death pandemic has identified key genetic differences that determined who lived and who died, and how those aspects of our immune systems have continued to evolve since that time.

Researchers from McMaster University, the University of Chicago, the Pasteur Institute and other organizations analyzed and identified genes that protected some against the devastating bubonic plague pandemic that swept through Europe, Asia and Africa nearly 700 years ago. Their study has been published in the journal Nature.

The same genes that once conferred protection against the Black Death are today associated with an increased susceptibility to autoimmune diseases such as Crohn’s and rheumatoid arthritis, the researchers report.

The team focused on a 100-year window before, during and after the Black Death, which reached London in the mid-1300s. It remains the single greatest human mortality event in recorded history, killing upwards of 50 per cent of the people in what were then some of the most densely populated parts of the world.

tooth Black Death shaped evolution of immunity genes, setting course for how we respond to disease today — Using DNA extracted from teeth of people who died before, during and after the Black Death pandemic, researchers were able to identify genetic differences that dictated who survived and who died from the virus. Credit: Matt Clarke/McMaster University

Researchers extracted DNA from the remains of people buried in the East Smithfield plague pits, which were used for mass burials in 1348 and 1349. Courtesy: Museum of London Archaeology (MOLA)

Black Death shaped evolution of immunity genes, setting course for how we respond to disease today — Researchers extracted DNA from the remains of people buried in the East Smithfield plague pits, which were used for mass burials in 1348 and 1349. Courtesy: Museum of London Archaeology (MOLA)

Evolutionary geneticist Hendrik Poinar has authored a new study, based on seven years of research, which found the genes that protected people against Black Death are associated with an increased susceptibility to autoimmune diseases. Credit: JD Howell/McMaster University

Members of the Barreiro lab conduct cell culture experiments. Courtesy: University of Chicago

More than 500 ancient DNA samples were extracted and screened from the remains of individuals who had died before the plague, died from it or survived the Black Death in London, including individuals buried in the East Smithfield plague pits used for mass burials in 1348-9. Additional samples were taken from remains buried in five other locations across Denmark.

Scientists searched for signs of genetic adaptation related to the plague, which is caused by the bacterium Yersinia pestis.

They identified four genes that were under selection, all of which are involved in the production of proteins that defend our systems from invading pathogens and found that versions of those genes, called alleles, either protected or rendered one susceptible to plague.

Individuals with two identical copies of a particular gene, known as ERAP2, survived the pandemic at a much higher rates than those with the opposing set of copies, because the ‘good’ copies allowed for more efficient neutralization of Y. pestis by immune cells.

“When a pandemic of this nature – killing 30 to 50 per cent of the population – occurs, there is bound to be selection for protective alleles in humans, which is to say people susceptible to the circulating pathogen will succumb. Even a slight advantage means the difference between surviving or passing. Of course, those survivors who are of breeding age will pass on their genes,” explains evolutionary geneticist Hendrik Poinar, an author of the Nature paper, director of McMaster’s Ancient DNA Centre, and a principal investigator with the Michael G. DeGroote Institute for Infectious Disease Research and McMaster’s Global Nexus for Pandemics & Biological Threats.

Europeans living at the time of the Black Death were initially very vulnerable because they had had no recent exposure to Yersinia pestis. As waves of the pandemic occurred again and again over the following centuries, mortality rates decreased.

Researchers estimate that people with the ERAP2 protective allele (the good copy of the gene, or trait), were 40 to 50 per cent more likely to survive than those who did not.

“The selective advantage associated with the selected loci are among the strongest ever reported in humans showing how a single pathogen can have such a strong impact to the evolution of the immune system,” says human geneticist Luis Barreiro, an author on the paper, and professor in Genetic Medicine at the University of Chicago.

The team reports that over time our immune systems have evolved to respond in different ways to pathogens, to the point that what had once been a protective gene against plague in the Middle Ages is today associated with increased susceptibility to autoimmune diseases. This is the balancing act upon which evolution plays with our genome.

“This highly original work has been possible only through a successful collaboration between very complementary teams working on ancient DNA, on human population genetics and the interaction between live virulent Yersinia pestis and immune cells,” says Javier Pizarro-Cerda, head of the Yersinia Research Unit and director of the World Health Organization Collaborating Centre for Plague at the Pasteur Institute.

“Understanding the dynamics that have shaped the human immune system is key to understanding how past pandemics, like the plague, contribute to our susceptibility to disease in modern times,” says Poinar.

The findings, the result of seven years of work from graduate student Jennifer Klunk, formally of McMaster’s Ancient DNA Centre and postdoctoral fellow Tauras Vigylas, from the University of Chicago, allowed for an unprecedented look at the immune genes of victims of the Black Death.

The research was funded in part by the Social Sciences and Humanities Research Council of Canada (SSHRC), The National Institutes of Health (NIH) and the Canadian Institute for Advanced Research, under the Humans and the Microbiome program.

Press release from McMaster University, by Michelle Donovan on how the Black Death shaped the evolution of immunity genes, setting course for how we respond to disease today.

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Biology

Fish fossils of Tujiaaspis vividus breathe new life into fin and limb evolutionary hypothesis

By ScientifiCult 29 September 2022

Fish Fossils of Tujiaaspis vividus Breathe New Life into Fin and Limb Evolutionary Hypothesis

A trove of fossils, unearthed in rock from China dating back some 436 million years, has revealed for the first time that the mysterious galeaspids, members of an extinct clade of jawless fish, possessed paired fins.

The discovery, by an international team led by Prof. ZHU Min from the Institute of Vertebrate Palaeontology and Palaeoanthropology (IVPP) of the Chinese Academy of Sciences and Prof. Philip Donoghue from the University of Bristol, shows the primitive condition of paired fins before they separated into pectoral and pelvic fins, the forerunner of arms and legs.

The findings were published in Nature on Sept. 28.

Fish fossils of Tujiaaspis vividus breathe new life into fin and limb evolutionary hypothesis. Fig. 1 Life reconstructions of Tujiaaspis vividus (Image by ZHENG Qiuyang)

Until now, the only surviving galeaspid fossils were heads, but these new fossils comprise whole bodies. They were found in rocks in Hunan Province and Chongqing and were named Tujiaaspis after the indigenous Tujia people who live in the region.

Fig. 3 The holotype specimen and its interpretative drawing of Tujiaaspis vividus from 436 million years old rocks of Chongqing, China (Image by Gai, et al.)

Theories abound about the evolutionary beginnings of vertebrate fins and limbs—the evolutionary precursors of arms and legs—and are mostly based on comparative embryology. There is a rich fossil record of early vertebrate , but they either had separated paired fins or they didn’t. There has been little evidence for the gradual evolution of fins.

According to first author GAI Zhikun, a professor at IVPP, “The anatomy of galeaspids has been something of a mystery since they were first discovered more than half a century ago. Tens of thousands of fossils are known from China and Vietnam, but almost all of them are just heads—nothing has been known about the rest of their bodies—until now.”

The new fossils are spectacular, preserving the whole body for the first time and revealing that these animals possessed paired fins that extended all the way from the back of the head to the very tip of the tail. This is a great surprise since scientists had thought galeaspids lack paired fins altogether.

“Tujiaaspis breathes new life into a century old hypothesis for the evolution of paired fins, through differentiation of pectoral (arms) and pelvic (legs) fins over evolutionary time from a continuous head-to-tail fin precursor,” said corresponding author Prof. Donoghue.

This “fin-fold” hypothesis has been very popular, but it has lacked any supporting evidence until now. The discovery of Tujiaaspis resurrects the fin-fold hypothesis and reconciles it with contemporary data on genetic control of the embryonic development of fins in living vertebrates.

Tujiaaspis shows the “primitive condition” for the evolution of paired fins, according to Prof. ZHU, who said that later jawless fish showed the first evidence for the separation of this fin-fold into pectoral and pelvic fins. Prof. ZHU also noted that the vestiges of elongate fin-folds could be seen in the embryos of living jawed fishes, which could be manipulated to produce them.

Fig. 2 3D reconstruction of Tujiaaspis vividus (Image by YANG Dinghua)

Bristol’s Dr. Humberto Ferron, a co-author, used computational engineering approaches to simulate the behaviour of models of Tujiaaspis with and without the paired fins. He said,

“The paired fins of Tujiaaspis act as hydrofoils, passively generating lift for the fish without any muscular input from the fins themselves. The lateral fin-folds of Tujiaaspis allowed it to swim more efficiently.”

“Our new analyses suggest that the ancestor of jawed vertebrates likely possessed paired fin-folds, which became separated into pectoral and pelvic regions,” said co-author Dr. Joseph Keating from the University of Bristol.

He noted that the primitive fins evolved musculature and skeletal support that allowed our fish ancestor to better steer their swimming and add propulsion.

“It is amazing to think that the evolutionary innovations seen in Tujiaaspis underpin locomotion in animals as diverse as birds, whales, bats, and humans,” he said.

Press release from the Chinese Academy of Sciences

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Biology

Fanjingshania renovata, Ancient ‘Shark’ from China Is Humans’ Oldest Jawed Ancestor

By ScientifiCult 29 September 2022

Fanjingshania renovata, an Ancient ‘Shark’ from China Is Humans’ Oldest Jawed Ancestor

Palaeontologists discover a 439-million-year-old ‘shark’ that forces us to rethink the timeline of vertebrate evolution

Living sharks are often portrayed as the apex predators of the marine realm. Paleontologists have been able to identify fossils of their extinct ancestors that date back hundreds of millions of years to a time known as the Palaeozoic period. These early “sharks,” known as acanthodians, bristled with spines. In contrast to modern sharks, they developed bony “armor” around their paired fins.

A recent discovery of a new species of acanthodian from China surprised scientists with its antiquity. The find predates by about 15 million years the earliest acanthodian body fossils and is the oldest undisputed jawed fish.

These findings were published in Nature on Sept. 28.

Fanjingshania renovata, an ancient 'Shark' from China is Humans' oldest jawed ancestor; the study has been published on Nature — Fig. 1 Life reconstruction of Fanjingshania renovata. (Image by ZHANG Heming)

Reconstructed from thousands of tiny skeletal fragments, Fanjingshania, named after the famous UNESCO World Heritage Site Fanjingshan, is a bizarre fish with an external bony “armor” and multiple pairs of fin spines that set it apart from living jawed fish, cartilaginous sharks and rays, and bony ray- and lobe-finned fish.

Examination of Fanjingshania by a team of researchers from the Chinese Academy of Sciences, Qujing Normal University, and the University of Birmingham revealed that the species is anatomically close to groups of extinct spiny “sharks” collectively known as acanthodians. Unlike modern sharks, acanthodians have skin ossifications of the shoulder region that occur primitively in jawed fish.

Fig. 3 Life reconstruction of Fanjingshania renovata. (Image by FU Boyuan and FU Baozhong)

The fossil remains of Fanjingshania were recovered from bone bed samples of the Rongxi Formation at a site in Shiqian County of Guizhou Province, South China.

These findings present tangible evidence of a diversification of major vertebrate groups tens of millions of years before the beginning of the so called “Age of Fishes” some 420 million years ago.

Fig. 4 Fragment of the pectoral dermal skeleton (part of a pectoral spine fused to shoulder girdle plate) of Fanjingshania renovata shown in ventral view. (Image by Andreev, et al.)

The researchers identified features that set apart Fanjingshania from any known vertebrate. It has dermal shoulder girdle plates that fuse as a unit to a number of spines—pectoral, prepectoral and prepelvic. Additionally, it was discovered that the ventral and lateral portions of the shoulder plates extend to the posterior edge of the pectoral fin spines. The species has distinct trunk scales with crowns composed of a row of tooth-like elements (odontodes) adorned by discontinuous nodose ridges. Peculiarly, dentine development is recorded in the scales but is missing in other components of the dermal skeleton such as the fin spines.

“This is the oldest jawed fish with known anatomy,” said Prof. ZHU Min from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences. “The new data allowed us to place Fanjingshania in the phylogenetic tree of early vertebrates and gain much needed information about the evolutionary steps leading to the origin of important vertebrate adaptations such as jaws, sensory systems, and paired appendages.”

From the outset, it was clear to the scientists that Fanjingshania’s shoulder girdle, with its array of fin spines, is key to pinpointing the new species’ position in the evolutionary tree of early vertebrates. They found that a group of acanthodians, known as climatiids, possess the full complement of shoulder spines recognized in Fanjingshania. What is more, in contrast to normal dermal plate development, the pectoral ossifications of Fanjingshania and the climatiids are fused to modified trunk scales. This is seen as a specialization from the primitive condition of jawed vertebrates where the bony plates grow from a single ossification center.

Unexpectedly, the fossil bones of Fanjingshania show evidence of extensive resorption and remodelling that are typically associated with skeletal development in bony fish, including humans.

“This level of hard tissue modification is unprecedented in chondrichthyans, a group that includes modern cartilaginous fish and their extinct ancestors,” said lead author Dr. Plamen Andreev, a researcher at Qujing Normal University. “It speaks about greater than currently understood developmental plasticity of the mineralized skeleton at the onset of jawed fish diversification.”

The resorption features of Fanjingshania are most apparent in isolated trunk scales that show evidence of tooth-like shedding of crown elements and removal of dermal bone from the scale base. Thin-sectioned specimens and tomography slices show that this resorptive stage was followed by deposition of replacement crown elements. Surprisingly, the closest examples of this skeletal remodelling are found in the dentition and skin teeth (denticles) of extinct and living bony fish. In Fanjingshania, however, the resorption did not target individual teeth or denticles, as occurred in bony fish, but instead removed an area that included multiple scale denticles. This peculiar replacement mechanism more closely resembles skeletal repair than the typical tooth/denticle substitution of jawed vertebrates.

A phylogenetic hypothesis for Fanjingshania that uses a numeric matrix derived from observable characters confirmed the researchers’ initial hypothesis that the species represents an early evolutionary branch of primitive chondrichthyans. These results have profound implications for our understanding of when jawed fish originated since they align with morphological clock estimates for the age of the common ancestor of cartilaginous and bony fish, dating it to around 455 million years ago, during a period known as the Ordovician.

These results tell us that the absence of undisputed remains of jawed fish of Ordovician age might be explained by under sampling of sediment sequences of comparable antiquity. They also point towards a strong preservation bias against teeth, jaws, and articulated vertebrate fossils in strata coeval with Fanjingshania.

“The new discovery puts into question existing models of vertebrate evolution by significantly condensing the timeframe for the emergence of jawed fish from their closest jawless ancestors. This will have profound impact on how we assess evolutionary rates in early vertebrates and the relationship between morphological and molecular change in these groups,” said Dr. Ivan J. Sansom from the University of Birmingham.

Press release from the Chinese Academy of Sciences

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Biology

Rare Fossil Teeth from China Overturn Long-held Views about Evolution of Vertebrates

By ScientifiCult 29 September 2022

Rare Fossil Teeth from China Overturn Long-held Views about Evolution of Vertebrates

An international team of researchers has discovered 439-million-year-old remains of a toothed fish that suggest the ancestors of modern osteichthyans (ray- and lobe-finned fish) and chondrichthyans (sharks and rays) originated much earlier than previously thought.

Related findings were published in Nature on Sept. 28.

Rare Fossil Teeth from China Overturn Long-held Views about Evolution of Vertebrates. Fig. 1 Life reconstruction of Qianodus duplicis. (Image by ZHANG Heming)

A remote site in Guizhou Province of south China, containing sequences of sedimentary layers from the distant Silurian period (around 445 to 420 million years ago), has produced spectacular fossil finds, including isolated teeth identified as belonging to a new species (Qianodus duplicis) of primitive jawed vertebrate. Named after the ancient name for modern-day Guizhou, Qianodus possessed peculiar spiral-like dental elements carrying multiple generations of teeth that were added throughout the life of the animal.

The tooth spirals (or whorls) of Qianodus turned out to be one of the least common fossils recovered from the site. They are small elements that rarely reach 2.5 mm and as such had to be studied under magnification with visible light and X-ray radiation.

A conspicuous feature of the whorls is that they contained a pair of teeth rows set into a raised medial area of the whorl base. These so-called primary teeth show an incremental increase in size towards the inner (lingual) portion of the whorl. What makes the whorls of Qianodus unusual in comparison with those of other vertebrates is the clear offset between the two primary teeth rows. A similar arrangement of neighboring teeth rows is also seen in the dentitions of some modern sharks but has not been previously identified in the tooth whorls of fossil species.

The discovery indicates that the well-known jawed vertebrate groups from the so-called “Age of Fishes” (420 to 460 million years ago) were already established some 20 million years earlier.

“Qianodus provides us with the first tangible evidence for teeth, and by extension jaws, from this critical early period of vertebrate evolution,” said LI Qiang from Qujing Normal University.

Unlike the continuously shedding teeth of modern sharks, the researchers believe that the tooth whorls of Qianodus were kept in the mouth and increased in size as the animal grew. This interpretation explains the gradual enlargement of replacement teeth and the widening of the whorl base as a response to the continuous increase in jaw size during development.

For the researchers, the key to reconstructing the growth of the whorls was two specimens at an early stage of formation, easily identified by their noticeably smaller sizes and fewer teeth. A comparison with the more numerous mature whorls provided the palaeontologists with a rare insight into the developmental mechanics of early vertebrate dentitions. These observations suggest that primary teeth were the first to form whereas the addition of the lateral (accessory) whorl teeth occurred later in development.

Fig. 2 Volumetric reconstruction of a tooth whorl viewed from its lingual side (holotype of Qianodus duplicis). The specimen is just over 2 mm in length. (Image by Zhu, et al.)

“Despite their peculiarities, tooth whorls have, in fact, been reported in many extinct chondrichthyan and osteichthyan lineages,”said Plamen Andreev, the lead author of the study. “Some of the early chondrichthyans even built their dentition entirely from closely spaced whorls.”

The researchers claim that this was also the case for Qianodus. They made this conclusion after examining the small (1–2 mm long) whorls of the new species with synchrotron radiation—a CT scanning process that uses high energy X-rays from a particle accelerator.

“We were astonished to discover that the tooth rows of the whorls have a clear left or right offset, which indicates positions on opposing jaw rami,” said Prof. ZHU Min from the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences.

Fig. 3 Virtual section along the length of a tooth whorl in side view (holotype of Qianodus duplicis). The specimen is just over 2 mm in length (Image by Zhu, et al.)

These observations are supported by a phylogenetic tree that identifies Qianodus as a close relative to extinct chondrichthyan groups with whorl-based dentitions.

“Our revised timeline for the origin of the major groups of jawed vertebrates agrees with the view that their initial diversification occurred in the early Silurian,” said Prof. ZHU.

The discovery of Qianodus provides tangible proof for the existence of toothed vertebrates and shark-like dentition patterning tens of millions of years earlier than previously thought. The phylogenetic analysis presented in the study identifies Qianodus as a primitive chondrichthyan, implying that jawed fish were already quite diverse in the Lower Silurian and appeared shortly after the evolution of skeletal mineralization in ancestral lineages of jawless vertebrates.

“This puts into question the current evolutionary models for the emergence of key vertebrate innovations such as teeth, jaws, and paired appendages,” said Ivan Sansom, a co-author of the study from the University of Birmingham.

Press release from the Chinese Academy of Sciences about the fossil teeth overturning long-held views on the evolution of vertebrates

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Biology

Dawn of Fishes — Early Silurian Jawed Vertebrates Revealed Head to Tail

By ScientifiCult 29 September 2022

Dawn of Fishes — Early Silurian Jawed Vertebrates Revealed Head to Tail

A newly discovered fossil “treasure hoard” dating back some 436 million years to the early Silurian period reveals, for the first time, the complete body shape and form of some of the first jawed fishes.

The discovery was published in Nature on Sept. 28 by an international team led by Prof. ZHU Min from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences and Prof. Per E. Ahlberg from Uppsala University, as the cover story and one in a series of four papers in the same issue.

The Gnathostomata or jawed vertebrates, which include not only almost all the backboned animals you see in zoos and aquariums but humankind as well, have a mysterious origin. The so-called molecular clock, which deduces the age of the most recent common ancestor of two animals by evaluating the difference between the two sets of DNA, suggests that the most recent common ancestor of all modern jawed vertebrates lived 450 million years ago during the Ordovician period. As a result, the origin of jaws cannot be later than that.

However, the fossil record of jawed vertebrates only becomes abundant from the Early Devonian (~419 million years ago), i.e., the beginning of the “Age of Fishes.” Only in the past 10 years have scientists found several complete jawed fishes from the Late Silurian (~425 million years ago). Even so, these records are still more than 25 million years later than when jaws should have originated. The dearth of earlier fossils means that jawed vertebrates are a “ghost lineage” in the early Silurian.

The remarkable discovery of complete early Silurian jawed fishes is the result of 20 years of continuous effort by the authors searching for fossil fishes in all possible Silurian rock strata in China. The breakthrough was finally made in late 2020, when complete early Silurian fishes were found in Xiushan County, Chongqing.

LI Qiang and CHEN Yang, both co-authors and leaders of the fieldtrips, recalled their research:

“We remember it was a rainy day. We climbed a mountain ghat. At the 38^th turn we found a complete Silurian fish, which initiated an explosion of discoveries in this area in the next two years.”

Fig. 1 Life reconstruction of Xiushanosteus mirabilis (Image by ZHANG Heming)

The authors reported two species. The first one and the most abundant species was named Xiushanosteus mirabilis. It is a tiny, 3-cm-long placoderm or armored jawed fish. The flat and semicircular head, along with the trunk armor, are reminiscent of its jawless ancestors, but its paired fins and powerful tail made Xiushanosteus a much more capable swimmer.

First author ZHU You’an, associate research professor at IVPP and also an Uppsala University alumnus, said,

“As a placoderm expert, I am dazzled by the early age and completeness of Xiushanosteus. It is like a dream. A lot of the anatomical features make perfect sense; it was an ‘Oh, now I know’ moment in my career.”

Fig. 2 Life reconstruction of Shenacanthus vermiformis (Image by ZHANG Heming)

The second fish reported is named Shenacanthus vermiformis. Also very small, it is an early shark relative. However, all the sharks we know are covered in tiny scales, or at most small mosaic plates. Shenacanthus instead has prominent “shoulder armor” made of several large plates that completely encircle its body. This feature, thought to be exclusive in placoderms, provides a strong hint that the first cartilaginous fishes were armored, similar to placoderms.

“Only 20 years ago it was still believed that sharks are primitive and other jawed fish evolved from a shark-like archetype. Now with the discovery of Shenacanthus, we can finally make certain that the opposite is true,” said Prof. ZHU You’an.

“Previously we could only dream of such exceptional and early fossils,” said corresponding author Prof. Ahlberg. “However, they are more than curiosities; they are first and foremost crucial data to test—and either support or confound—our long-held hypotheses regarding the rise of our lineage.”

“The excavation continues to yield remarkable materials,” said Prof. ZHU Min, who led the project and is also a CAS academician. “The Chongqing Lagerstätte, like the Chengjiang and Jehol biotas, will become a world-famous paleontological heritage and will provide key evidence for how the extraordinary diversity of the jawed vertebrates we see today arose.”

Press release from the Chinese Academy of Sciences

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Astronomy

Supermassive Black Hole Precursor Detected in Archival Hubble Data

By ScientifiCult 13 April 2022

Supermassive Black Hole Precursor Detected in Archival Hubble Data

An international team of astronomers using archival data from the NASA/ESA Hubble Space Telescope and other space- and ground-based observatories have discovered a unique object in the distant, early Universe that is a crucial link between star-forming galaxies and the emergence of the earliest supermassive black holes. This object is the first of its kind to be discovered so early in the Universe’s history, and had been lurking unnoticed in one of the best-studied areas of the night sky.

Astronomers have struggled to understand the emergence of supermassive black holes in the early Universe ever since these objects were discovered at distances corresponding to a time only 750 million years after the Big Bang [1]. Rapidly growing black holes in dusty, early star-forming galaxies are predicted by theories and computer simulations but until now they had not been observed. Now, however, astronomers have reported the discovery of an object — which they name GNz7q — that is believed to be the first such rapidly growing black hole to be found in the early Universe. Archival Hubble data from the Advanced Camera for Surveys helped the team study the compact ultraviolet emission from the black hole’s accretion disc and to determine that GNz7q existed just 750 million years after the Big Bang.

“Our analysis suggests that GNz7q is the first example of a rapidly-growing black hole in the dusty core of a starburst galaxy at an epoch close to the earliest super massive black hole known in the Universe,” explains Seiji Fujimoto, an astronomer at the Niels Bohr Institute of the University of Copenhagen in Denmark and lead author of the paper describing this discovery. “The object’s properties across the electromagnetic spectrum are in excellent agreement with predictions from theoretical simulations.”

Supermassive Black Hole Precursor Detected in Archival Hubble Data: Crop of the GNz7q in the Hubble GOODS-North field. An international team of astronomers using archival data from the NASA/ESA Hubble Space Telescope and other space- and ground-based observatories have discovered a unique object in the distant, early Universe that is a crucial link between young star-forming galaxies and the earliest supermassive black holes. This object is the first of its kind to be discovered so early in the Universe’s history, and had been lurking unnoticed in one of the best-studied areas of the night sky. The object, which is referred to as GNz7q, is shown here in the centre of the image of the Hubble GOODS-North field. **Credit:** NASA, ESA, G. Illingworth (University of California, Santa Cruz), P. Oesch (University of California, Santa Cruz; Yale University), R. Bouwens and I. Labbé (Leiden University), and the Science Team, S. Fujimoto et al. (Cosmic Dawn Center [DAWN] and University of Copenhagen)

Current theories predict that supermassive black holes begin their lives in the dust-shrouded cores of vigorously star-forming “starburst” galaxies before expelling the surrounding gas and dust and emerging as extremely luminous quasars. Whilst they are extremely rare, examples of both dusty starburst galaxies and luminous quasars have been detected in the early Universe. The team believes that GNz7q could be the “missing link” between these two classes of objects.

“GNz7q provides a direct connection between these two rare populations and provides a new avenue towards understanding the rapid growth of supermassive black holes in the early days of the Universe,” continued Fujimoto. “Our discovery is a precursor of the supermassive black holes we observe at later epochs.”

Whilst other interpretations of the team’s data cannot be completely ruled out, the observed properties of GNz7q are in strong agreement with theoretical predictions. GNz7q’s host galaxy is forming stars at the rate of 1600 solar masses of stars per year [2] and GNz7q itself appears bright at ultraviolet wavelengths but very faint at X-ray wavelengths. The team have interpreted this — along with the host galaxy’s brightness at infrared wavelengths — to suggest that GNz7q is harbors a rapidly growing black hole still obscured by the dusty core of its accretion disc at the center of the star-forming host galaxy.

Supermassive Black Hole Precursor Detected in Archival Hubble Data: GNz7q in the Hubble GOODS-North field. An international team of astronomers using archival data from the NASA/ESA Hubble Space Telescope and other space- and ground-based observatories have discovered a unique object in the distant, early Universe that is a crucial link between young star-forming galaxies and the earliest supermassive black holes. This object is the first of its kind to be discovered so early in the Universe’s history, and had been lurking unnoticed in one of the best-studied areas of the night sky. The object, which is referred to as GNz7q, is shown here in the centre of the cutout from the Hubble GOODS-North field. **Credit:** NASA, ESA, G. Illingworth (University of California, Santa Cruz), P. Oesch (University of California, Santa Cruz; Yale University), R. Bouwens and I. Labbé (Leiden University), and the Science Team, S. Fujimoto et al. (Cosmic Dawn Center [DAWN] and University of Copenhagen)

As well as GNz7q’s importance to the understanding of the origins of supermassive black holes, this discovery is noteworthy for its location in the Hubble GOODS North field, one of the most highly scrutinised areas of the night sky [3].

“GNz7q is a unique discovery that was found just at the centre of a famous, well-studied sky field — showing that big discoveries can often be hidden just in front of you,” commented Gabriel Brammer, another astronomer from the Niels Bohr Institute of the University of Copenhagen and a member of the team behind this result. “It’s unlikely that discovering GNz7q within the relatively small GOODS-N survey area was just ‘dumb luck’ rather the prevalence of such sources may in fact be significantly higher than previously thought.”

Finding GNz7q hiding in plain sight was only possible thanks to the uniquely detailed, multi-wavelength datasets available for GOODS-North. Without this richness of data GNz7q would have been easy to overlook, as it lacks the distinguishing features usually used to identify quasars in the early Universe. The team now hopes to systematically search for similar objects using dedicated high-resolution surveys and to take advantage of the NASA/ESA/CSA James Webb Space Telescope’s spectroscopic instruments to study objects such as GNz7q in unprecedented detail.

“Fully characterising these objects and probing their evolution and underlying physics in much greater detail will become possible with the James Webb Space Telescope.” concluded Fujimoto. “Once in regular operation, Webb will have the power to decisively determine how common these rapidly growing black holes truly are.”

Notes

[1] Whilst light travels imperceptibly quickly in day-to-day life, the vast distances in astronomy mean that as astronomers look at increasingly distant objects, they are also looking backwards in time. For example, light from the Sun takes around 8.3 minutes to reach Earth, meaning that we view the Sun as it was 8.3 minutes ago. The most distant objects are the furthest back in time, meaning that astronomers studying very distant galaxies are able to study the earliest periods of the Universe.

[2] This does not mean that 1600 Sun-like stars are produced each year in GNz7q’s host galaxy, but rather that a variety of stars are formed each year with a total mass 1600 times that of the Sun.

[3] GOODS — the Great Observatories Origins Deep Survey — is an astronomical survey that combines multi-wavelength observations from some of the most capable telescopes ever built, including Hubble, ESA’s Herschel and XMM-Newton space telescopes, NASA’s Spitzer Space Telescope and Chandra X-ray Observatory, and powerful ground-based telescopes.

Supermassive Black Hole Precursor: more information

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

These results have been published in Nature.

The international team of astronomers in this study consists of S. Fujimoto (Cosmic Dawn Center [DAWN] and Niels Bohr Institute, University of Copenhagen, Denmark), G. B. Brammer (DAWN and Niels Bohr Institute, University of Copenhagen, Denmark), D. Watson (DAWN and Niels Bohr Institute, University of Copenhagen, Denmark), G. E. Magdis (DAWN, DTU-Space at the Technical University of Denmark, and Niels Bohr Institute at the University of Copenhagen, Denmark), V. Kokorev (DAWN and Niels Bohr Institute, University of Copenhagen, Denmark), T. R. Greve (DAWN and DTU-Space, Technical University of Denmark, Denmark), S. Toft (DAWN and Niels Bohr Institute, University of Copenhagen, Denmark), F. Walter ( DAWN, Denmark, the Max Planck Institute for Astronomy, Germany, and the National Radio Astronomy Observatory, USA), R. Valiante (INAF-Osservatorio Astronomico di Roma, Rome, Italy), M. Ginolfi (European Southern Observatory, Garching, Germany), R. Schneider (INAF-Osservatorio Astronomico di Roma, Rome, Italy and Dipartimento di Fisica, Universitá di Roma La Sapienza, Rome, Italy), F. Valentino (DAWN and Niels Bohr Institute, University of Copenhagen, Denmark), L. Colina (DAWN, Copenhagen, Denmark and Centro de Astrobiología (CAB, CSIC-INTA), Madrid, Spain), M. Vestergaard (Niels Bohr Institute, University of Copenhagen, Denmark, and Steward Observatory, University of Arizona, USA), R. Marques-Chaves (Geneva Observatory, University of Geneva, Switzerland), J. P. U. Fynbo (DAWN and Niels Bohr Institute, University of Copenhagen, Denmark), M. Krips (IRAM, Domaine Universitaire, Saint-Martin-d’Hères, France), C. L. Steinhardt (DAWN and Niels Bohr Institute, University of Copenhagen, Denmark), I. Cortzen (IRAM, Domaine Universitaire, Saint-Martin-d’Hères, France), F. Rizzo (DAWN and Niels Bohr Institute, University of Copenhagen, Denmark), and P. A. Oesch (DAWN, Copenhagen, Denmark and Geneva Observatory, University of Geneva, Switzerland).

Press release from ESA/Hubble Information Centre

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